Phase synchronizing pulse amplitude modulation fluorometer

ABSTRACT

A phase synchronizing pulse amplitude modulation fluorometer having an excitation light source capable of emitting a pulse of light that will induce fluorescence in an external object. A photo detector for detecting the pulse and a circuit to synchronize a pulse of light from the excitation light source with a pulse of light from an external light source.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of, and claims priority to,U.S. application Ser. No. 14/627,473 filed Feb. 20, 2015, which ishereby incorporated by reference in its entirety.

TECHNICAL FIELD

This invention relates generally to improvements in fluorometers. Amongother uses, the present invention may provide an improved fluorometerthat may be used to measure chlorophyll fluorescence to investigateplant physiology, allowing the optimization of lighting provided toplants.

BACKGROUND OF THE INVENTION

Fluorometers have a wide variety of uses. By way of example, and not tolimit the scope of the invention, fluorometers are used to measurechlorophyll fluorescence to investigate plant physiology and in thedairy industry to verify whether pasteurization has been successful.

In some fluorometry applications, there may be a light source that ispulsed. The fluorescence of an external object may vary depending on theapplication of the light source. For example, and not to limit the scopeof the invention, the fluorescence of an external object may be strongwhen the light pulse is on, and less strong when the light pulse is off.As a further example, and not meant to limit the invention, when plantsare grown with one or more electrically powered lights, it may bedesirable to pulse the light source. In all applications using a pulsedlight, it is useful to be able to measure and thereby understand thefluorescence at all phases of the pulsed light. Existing fluorometers donot have that capability. Among other advantages, and not meant to belimiting, the present invention provides that capability.

SUMMARY OF THE INVENTION

The present invention may include a phase synchronizing pulse amplitudemodulation fluorometer, or PSPAMF. The PSPAMF of the present inventionmay include an excitation light source capable of inducing fluorescencein an external object, a fluorescence detector for detectingfluorescence in an external obj ect, and a circuit to synchronize apulse of light from the excitation light source with a pulse of lightfrom an external light source. The PSPAMF may include embodiments wherethe external light source is included as a part of the PSPAMF. In theseembodiments, the circuit to synchronize the excitation light source witha pulse generated by the external light source may include an electronicconnection between the external light source and the excitation lightsource. The electrical connection between the external light source andthe excitation light source may be a wireless connection and it may be awired connection.

The PSPAMF may include embodiments where the external light source is apart of the PSPAMF and where the circuit to synchronize the excitationlight source with a pulse generated by the external light source makesuse of an external reference. In such embodiments, the external lightsource and the excitation light source may both be configured to detectthe external reference.

The PSPAMF may include embodiments where the external light source isnot provided. Such embodiments may include a photo detector fordetecting a pulse of light generated by the external light source. Thephoto detector may be in communication with the excitation light source,and may further be configured to cause the pulse of the excitation lightsource to correspond to one or more aspects of the pulse of the externallight source. For example, and not meant to be limiting, the photodetector may be in communication with the excitation light sourcethrough a phase synchronizing circuit. In this manner, the pulse of theexcitation light source may be configured to correspond to one or moreof the rising edge, the zero crossing, the falling edge, the variablefrequency, and the duty-cycle of the pulse generated by the externallight source. The photo detector and the excitation light source may bein communication with a microprocessor. The microprocessor may furtherbe configured to cause the excitation light source to produce a pulsethat corresponds to one or more aspects of the pulse of the externallight source. For example, and not meant to be limiting, themicroprocessor may cause the excitation light source to produce a pulsethat corresponds to one or more of the rising edge, the zero crossing,the falling edge, the variable frequency, and the duty-cycle of thepulse generated by the external light source.

As used herein, a fluorescence detector is any device that acts as anamplifying photodetector, including, without limitation, an avalanchephoto diode (APD) and a photo multiplier tube (PMT).

The excitation light source may be any light source capable ofgenerating a fluorescence response in the external object. For example,and not meant to be limiting, suitable light sources for the excitationlight source of the PSPAMF include narrow band width emittingsemiconductors; light emitting diodes; lasers; including a pulsed laser,a pumped laser, a diode-pumped solid-state laser, and a flashlamp pumpedlaser. Suitable light sources further include, but are not limited to, apulsed arc-discharge lamp; a xenon flashlamp; a xenon flashlamp incombination with an excitation filter; a continuous emmision lamp; atungsten halogen lamp; and a tungsten halogen lamp with anopto-mechanical interrupter and an excitation filter.

While not meant to limiting, in embodiments where the excitation lightsource is a laser diode, the power of the laser diode may be between 5mW and 200 mW.

While not meant to limiting, in embodiments where the PSPAMF is used toregulate light sources used for growing plants, the excitation lightsource may be a wavelength capable of promoting photosynthesis. Inembodiments where the excitation light source is a wavelength capable ofpromoting photosynthesis, the excitation light source may or may not bepowerful enough to promote photosynthesis.

While not meant to limiting, the excitation light source of the PSPAMFmay be a directly focused laser, or a laser in communication with afiber optic cable.

While not meant to limiting, the excitation light source of the PSPAMFmay be configured to provide a saturation pulse. As used herein, asaturation pulse is an intense pulse of actinic light capable ofmomentarily saturating a plants photosynthetic system.

While not meant to limiting, the fluorescence detector of the PSPAMF maybe an avalanche photo diode or a photo multiplier tube.

While not meant to limiting, the fluorescence detector of the PSPAMF maybe an avalanche photo diode having an active area between 500 μm and 800μm.

While not meant to limiting, the fluorescence detector of the PSPAMF maybe an avalanche photo diode in communication with an optical long passfilter. The avalanche photo diode may further be mounted into acollimator tube, the collimator tube may further hold a lens, the lensmay be aspherical, and the aspherical lens may be at an angle to a fiberoptic cable or a direct focused laser.

While not meant to limiting, the fluorescence detector of the PSPAMF maybe configured to measure the maximum fluorescence of the external objectduring saturation of the pulse.

While not meant to limiting, the photo detector of the PSPAMF may beconfigured to communicate at least one of the frequency, phase andduty-cycle of the pulse of the external light source to the phasesynchronizing circuit.

While not meant to limiting, the phase synchronizing circuit may includea microprocessor

While not meant to limiting, the photo detector of the PSPAMF may bewired to the circuit connecting the external light source with the phasesynchronizing circuit, or a wireless circuit may connect the externallight source with the phase synchronizing circuit.

While not meant to limiting, the photo detector of the PSPAMF may beconfigured to detect the intensity of the external light source. Thephoto detector of the the PSPAMF may be configured to detect at leastone of the rising edge, the zero crossing, the falling edge, thevariable frequency, and the duty-cycle of the pulse generated by anexternal light source.

While not meant to limiting, the phase synchronizing circuit of thePSPAMF may be configured to detect changes in the pulse generated by anexternal light source between 1 Hz and 1 MHz.

While not meant to limiting, the phase synchronizing circuit of thePSPAMF may be configured to detect changes in the pulse generated by anexternal light source between 0 and 100% duty-cycle.

While not meant to limiting, the phase synchronizing circuit of thePSPAMF may be configured to to adapt the excitation light to changes inthe pulse generated by an external light source between 1 Hz and 1 MHz.

While not meant to limiting, the phase synchronizing circuit of thePSPAMF may be configured to adapt the excitation light to changes in thepulse generated by an external light source between 0 and 100%duty-cycle.

While not meant to limiting, the fluorescence detector of the PSPAMF mayinclude operation in a single point mode wherein one or both of theexcitation light and the fluorescence detector are directed toward asingle location on the external object. For example, and not meant to belimiting, in a configuration where the PSPAMF is used to optimize theoperation of an indoor plant growing operation, one or both of theexcitation light and the fluorescence detector may be scanned on arepresentative spot in the vegetative matter, allowing the PSPAMF tosurvey the fluorescent response of that representative spot of thevegetative matter.

Conversely, and also not meant to be limiting, the fluorescence detectorof the PSPAMF may include operation in a scanning mode wherein one orboth of the excitation light and the fluorescence detector are directedtoward multiple locations on the external object. For example, and notmeant to be limiting, in a configuration where the PSPAMF is used tooptimize the operation of an indoor plant growing operation, one or bothof the excitation light and the fluorescence detector may be scannedacross a large volume of vegetative matter in the growing area, allowingthe PSPAMF to survey the fluorescent response across the entire volumeof vegetative matter.

As a further example, and not meant to be limiting, the presentinvention may be operated in a greenhouse full of plants where it isdesirable to measure the fluorescence across a broad area of thegreenhouse. In such a configuration, the fluorescence detector may be acamera with a sensor having the capability to capture the image of alarge portion of the plants within the greenhouse, or all of the plantswithin the greenhouse, onto the camera's sensor. In such aconfiguration, the excitation light may be a single, wide-arc flash oflight across the plants in the greenhouse.

Alternatively, the fluorescence detector may be configured as a linearray of sensors with the capability to acquire fluorescence emissionalong a straight line in the field of view. In such a configuration, theexcitation light may be a single, wide-arc flash of light, with thesensor tilted to obtain the fluorescent response in a second dimension.

Yet another alternative is where the fluorescence detector is configuredto read the overall fluorescence from a wide field of view. Theexcitation source in such an arrangement may be from a collimated sourcethat sweeps the field of view, and the detected coordinates are obtainedfrom the direction in which the source points.

As used herein, the term “circuit” means a path in which electrons froma voltage or current source flow. Such circuits may include one or moremicroprocessors, which would also fall within the applicant's use of theterm “circuit” to describe an electrical path to synchronize a pulse ofthe excitation light source with a pulse of the external light source asused herein. The term circuit may further include an electrical paththat synchronizes the excitation light source with a pulse of theexternal light source and the detection of fluorescence. The circuitused to synchronize a pulse of the excitation light source with a pulseof the external light source as used herein may thus be accomplished ina variety of ways, all of which may be referred to herein as a “phasesynchronizing circuit.”

For example, and not meant to be limiting, each of the external lightsource and the excitation light source may include a circuit to controlone or more of the start, finish, duty cycle, duration, timing,frequency and intensity of a pulse of light generated by the externallight source and the excitation light, respectively. The circuit mayinclude a microprocessor programmed to provide each of these functions.Accordingly, a circuit may be provided in one or both the external lightsource and the excitation light source which may be configured tocommunicate directly with one and another by connecting the externallight source and the excitation light source. This may be accomplishedwith a wired or a wireless connection. In this manner, by way of exampleand not meant to be limiting, the external light source may beconfigured to communicate one or more of the start, finish, duty cycle,duration, timing, frequency and intensity of a pulse of light generatedby the external light source to the excitation light source. Theexcitation light source may then have a circuit configured tosynchronize a pulse generated by the excitation light source with thepulse generated by the external light source, using the informationcommunicated by the external light source.

Alternatively, the excitation light source may be configured tocommunicate one or more of the start, finish, duty cycle, duration,timing, frequency and intensity of a pulse of light generated by theexcitation light source to the external light source. The external lightsource may then be configured to include a circuit that will synchronizea pulse generated by the external light source with the pulse generatedby the excitation light source, using that communication.

In an analogous manner, the circuit to synchronize a pulse of theexcitation light source with a pulse of the external light source can beaccomplished by providing a photo detector that is capable of detectinga light pulse generated by the external light source. For example, andnot meant to be limiting, the excitation light source may include aphoto detector to detect one or more of the start, finish, duty cycle,duration, timing, frequency and intensity of a pulse of light generatedby the external light source. Accordingly, the excitation light sourcemay be configured to include a circuit connected to the photo detectorto synchronize a pulse of light with a pulse of light generated by theexternal light source.

Alternatively, by way of example and not meant to be limiting, theexcitation light source may be configured with a photo detector todetect one or more of the start, finish, duty cycle, duration, timing,frequency and intensity of a pulse of light generated by the externallight source. The excitation light source may further include a circuitconfigured to synchronize a pulse generated by the excitation lightsource with the pulse generated by the external light source that wasdetected by the photo detector connected to the excitation light source.Such a circuit would also fall within the applicant's use of the term“circuit” when describing and claiming a circuit to synchronize a pulseof the excitation light source with a pulse of the external lightsource.

As used herein, the circuit to synchronize a pulse of the excitationlight source with a pulse of the external light source may further makeuse of an external reference. As used herein, an “external reference”means any type of device, or a signal generated by such a device thatcan be detected by each of the external light source and the excitationlight source. While not meant to be limiting, examples of a suitableexternal reference would include any device capable of sending a signal,such a Global Positioning System, or so-called GPS, and the signalproduced by a GPS. A circuit connected to the external light source anda circuit connected to the excitation light source may then detect thesignal from the external reference, and then generate a pulse of theexternal light source and a pulse of the excitation light sourcesynchronized by timing one or more of the start, finish, duty cycle,duration, timing, frequency and intensity to one and another. Suchcircuits would also fall within the applicant's use of the term“circuit” to describe a “circuit” to synchronize a pulse of theexcitation light source with a pulse of the external light source asused herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the embodiments of the inventionwill be more readily understood when taken in conjunction with thefollowing drawings, wherein:

FIG. 1 is an illustration of one embodiment of the present invention.

FIG. 2 is an illustration of one embodiment of the present inventionwhere the excitation light source has a connection with the externallight source.

FIG. 3 is an illustration of one embodiment of the present inventionutilizing an external reference.

FIG. 4 is an illustration of one embodiment of the present inventionshowing the arrangement of an avalanche photo diode, optical long passfilter, lens, collimator tube, and fiber optic cable.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitations of the inventivescope is thereby intended, as the scope of this invention should beevaluated with reference to the claims appended hereto. Alterations andfurther modifications in the illustrated devices, and such furtherapplications of the principles of the invention as illustrated hereinare contemplated as would normally occur to one skilled in the art towhich the invention relates.

One exemplary embodiment of the present invention is shown in FIG. 1. Asshown in FIG. 1, a phase synchronizing pulse amplitude modulationfluorometer has an excitation light source 1 capable of emitting light 2that will induce fluorescence 3 in an external obj ect 4. A fluorescencedetector 5 for detecting fluorescence 2 in an external object 4 is alsoprovided. The present invention may further include a photo detector 9capable of detecting the pulse of light 7 from an external light source8. The photo detector 9 may be connected to a circuit 6 which in turnmay be connected to the excitation light source 1 that can synchronize apulse of light 2 from the excitation light source 1 with a pulse oflight 7 from an external light source 8. The circuit 6 may further beconnected to the fluorescence detector 5.

As shown in FIG. 2, the phase synchronizing pulse amplitude modulationfluorometer (PSPAMF) may include embodiments where the external lightsource 8 is included as a part of the PSPAMF. In these embodiments, thecircuit 6 to synchronize the excitation light source 1 with a pulse 7generated by the external light source 8 may include an electronicconnection 10 between the external light source 8 and the circuit 6. Theelectrical connection 10 between the external light source and theexcitation light source may be a wireless connection and it may be awired connection. The circuit 6 may further be connected to thefluorescence detector 5.

As shown in FIG. 3, the PSPAMF may include embodiments where theexternal light source 8 is a part of the PSPAMF and where the circuit 6to synchronize the excitation light source 1 with a pulse 7 generated bythe external light source 8 makes use of an external reference 11. Insuch embodiments, the external light source 8 and the excitation lightsource 1 may both be configured to detect signals 12 sent by theexternal reference 10. The circuit 6 may further be connected to thefluorescence detector 5.

As shown in FIG. 4, the fluorescence detector of the PSPAMF may includean avalanche photo diode 13 in communication with an optical long passfilter 14. The avalanche photo diode 13 may further be mounted into acollimator tube 15. The collimator tube 15 may further hold a lens 16,and the lens may be aspherical. A fiber optic cable 17 may provide light2 from the excitation light source 1, and may held at an angle 18 to theassembly of the avalanche photo diode 13, optical long pass filter 14,lens 16, and collimator tube 15.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character. Only certain embodimentshave been shown and described, and all changes, equivalents, andmodifications that come within the spirit of the invention describedherein are desired to be protected. Any experiments, experimentalexamples, or experimental results provided herein are intended to beillustrative of the present invention and should not be consideredlimiting or restrictive with regard to the invention scope. Further, anytheory, mechanism of operation, proof, or finding stated herein is meantto further enhance understanding of the present invention and is notintended to limit the present invention in any way to such theory,mechanism of operation, proof, or finding.

Thus, the specifics of this description and the attached drawings shouldnot be interpreted to limit the scope of this invention to the specificsthereof. Rather, the scope of this invention should be evaluated withreference to the claims appended hereto. In reading the claims it isintended that when words such as “a”, “an”, “at least one”, and “atleast a portion” are used there is no intention to limit the claims toonly one item unless specifically stated to the contrary in the claims.Further, when the language “at least a portion” and/or “a portion” isused, the claims may include a portion and/or the entire items unlessspecifically stated to the contrary. Likewise, where the term “input” or“output” is used in connection with an electric device or fluidprocessing unit, it should be understood to comprehend singular orplural and one or more signal channels or fluid lines as appropriate inthe context. Finally, all publications, patents, and patent applicationscited in this specification are herein incorporated by reference to theextent not inconsistent with the present disclosure as if each werespecifically and individually indicated to be incorporated by referenceand set forth in its entirety herein.

We claim: 1) A phase synchronizing pulse amplitude modulationfluorometer comprising, an excitation light source capable of inducingfluorescence in an external object; a fluorescence detector fordetecting fluorescence in an external object, an external light sourcecapable of generating a pulse of light, a photo detector for detecting apulse of light generated by an external light source, and a circuit tosynchronize a pulse of light from the excitation light source with apulse of light from the external light source. 2) The phasesynchronizing pulse amplitude modulation fluorometer of claim 1 whereinthe photo detector for detecting a pulse generated by an external lightsource is configured to communicate at least one of the frequency, phaseand duty-cycle of the pulse of the external light source to a phasesynchronizing circuit. 3) The phase synchronizing pulse amplitudemodulation fluorometer of claim 1 wherein a wired circuit connects theexternal light source with a phase synchronizing circuit and isconfigured to communicate at least one of the frequency, phase andduty-cycle of the pulse of the external light source to a phasesynchronizing circuit. 4) The phase synchronizing pulse amplitudemodulation fluorometer of claim 4 wherein a wireless circuit connectsthe external light source with a phase synchronizing circuit and isconfigured to communicate at least one of the frequency, phase andduty-cycle of the pulse of the external light source to a phasesynchronizing circuit. 5) The phase synchronizing pulse amplitudemodulation fluorometer of claim 1 wherein the photo detector fordetecting a pulse generated by an external light source is a photodiode.6) A phase synchronizing pulse amplitude modulation fluorometercomprising, an excitation light source capable of inducing fluorescencein an external object; a fluorescence detector for detectingfluorescence in an external object, an external light source capable ofgenerating a pulse of light, a photo detector for detecting a pulse oflight generated by an external light source, and a circuit tosynchronize a pulse of light from the excitation light source with apulse of light from the external light source wherein the photo detectorfor detecting a pulse generated by an external light source is incommunication with a phase synchronizing circuit. 7) The phasesynchronizing pulse amplitude modulation fluorometer of claim 6 whereinthe photo detector is configured to detect the intensity of the externallight source. 8) The phase synchronizing pulse amplitude modulationfluorometer of claim 6 wherein the phase synchronizing circuit isconfigured to determine at least one of the rising edge, the zerocrossing, the falling edge, the variable frequency, and the duty-cycleof the pulse generated by an external light source. 9) The phasesynchronizing pulse amplitude modulation fluorometer of claim 6, whereinthe phase synchronizing circuit is configured to detect changes in thepulse between 1 Hz and 1 MHz. 10) The phase synchronizing pulseamplitude modulation fluorometer of claim 6, wherein the phasesynchronizing circuit is configured to detect changes in the pulsebetween 0 and 100% duty-cycle. 11) The phase synchronizing pulseamplitude modulation fluorometer of claim 6, wherein the phasesynchronizing circuit is configured to adapt the excitation light tochanges in the pulse between 1 Hz and 1 MHz. 12) The phase synchronizingpulse amplitude modulation fluorometer of claim 6, wherein the phasesynchronizing circuit is configured to adapt the excitation light tochanges in the pulse between 0 and 100% duty-cycle.